This invention relates generally to microsurgical and ophthalmic systems and, particularly, to the field of ophthalmic surgical instruments, and more specifically, to a handpiece especially for scissors or forceps, which handpiece is actuated by a foot pedal controlled stepper motor and which provides the capability of transferring the rotary motion of the stepper motor output to linear motion, to thereby operate the surgical instrument.
Present day ophthalmic microsurgical systems provide one or more surgical instruments connected to a control console. The instruments are often electrically or pneumatically operated and the control console provides electrical or fluid pressure control signals for operating the instruments. The control console usually includes several different types of human actuable controllers for generating the control signals supplied to the surgical instruments. Often, the surgeon uses a foot pedal controller to remotely control the surgical instruments.
The use of intraocular surgical scissors is well known. While manually operated scissors are still in widespread use worldwide, they suffer from the disadvantage of being subject to human limitations on speed and accuracy. The use of surgical scissors with electric motor drive is also widespread. Electrical motor driven scissors are divided into two well known types based upon the type of drive, those that are solenoid actuated and those that are driven by a direct current motor or "proportional" control.
Most intraocular scissors have design similarities in which a pair of cutting blades extend from the end of a tubular needle with one blade being fixed and the other, opposed blade end being reciprocated between an open and a closed position with respect to the fixed blade. This reciprocating motion is accomplished through the action of one of the driving systems mentioned, such as, for example, a manual or electric motor drive.
Electric motor drivers of either rotary or linear solenoid type activate scissor closure by controlled transfer of the motor energy to the movable blade. The scissors may be of the vertical design (the guillotine, or the parallel blade type), the angled or horizontal-style, or of another design, or the driver may instead be used to actuate other instruments, besides scissors, that operate similarly (i.e., forceps).
The linear solenoid type of drive provides a reciprocating action in which the electrical actuation of a solenoid causes the movable blade to move to the closed position in relation to the fixed blade and then, usually through the operation of a spring, to return to the open position. An example of a handpiece of this type is seen in the patent which issued to Lo et al., U.S. Pat. No. 5,275,607.
One known example of a proportional control is seen in U.S. Pat. No. 4,757,814, which issued to Wang et al., for a proportional control for a pneumatic cutting device. However, that device, although disclosed as proportional, includes a linear solenoid valve actuated by a selectively varied electrical signal generated by a power supply and is controlled by a potentiometer which is in turn operated by a foot pedal.
The rotary electric motor drive may also be considered as a "proportional-cut" mode of operation because the motor is typically a stepper or rotary motor. The motion of the movable blade is controlled by the surgeon and the rate and amount of closure of the blade is proportional to the rate and amount of movement of the control device by the surgeon.